theft system problem

I have a 1996 sunfire. The speedometer is no longer working, i had the sensor replaced but still didnt fix the problem. I found out the problem was in the dashboard. I got a used speedometer cluster and when i put it in and tried to start the car, it wouldnt start, the theft system light came on. I put my old one back in and it started fine. Any help i can get on this will be appreciated.

Thank you
Chrissy

I got the problem fixed with the theft system, my car is starting fine now. I still have the same problem with the speedometer not working. IS there anything else I can try except what I've already done?

Thanks

What did you do to get the theft system fixed?
Steve